Topics in Geriatrics: Vestibular Screening, The Head-Shaking Nystagmus Test
The Head-Shaking Nystagmus (HSN) Test is a screening test used to identify unilateral vestibular hypofunction. It is appropriate for community-dwelling adults and older adults who exhibit signs and symptoms of vestibular dysfunction.
Objectives:
To provide basic and essential information regarding the HSN Test and vestibular testing.
To provide further information on modifications and equipment related to the HSN Test.
To provide new therapists with additional resources to facilitate more effective Vestibular Screening.
To provide patients, family, and caregivers with educational resources regarding vestibular testing.
To explore the evidence surrounding the HSN Test.
General Information
Head-shaking nystagmus (HSN) is latent, spontaneous eye movement elicited by rapid passive head shaking around a longitudinal axis. The HSN Test is a well-known clinical tool used to help confirm the presence of unilateral vestibular hypofunction. Procedure:
Instruct the patient to close their eyes
Flex patient’s head 30 deg
Passively oscillate patient’s head for 20 cycles at a frequency of 2 cycles per second, or 2 Hz (some sources suggest up to 30 cycles at 2 Hz)
Stop oscillations, have patient open their eyes, and check for nystagmus
Interpretation of positive test: If nystagmus is not present, normal vestibular function is indicated. If nystagmus is present, however, an asymmetry between the left and right peripheral vestibular inputs may be present. Typically, if unilateral vestibular hypofunction is present, eye movement will manifest as horizontal nystagmus, with the slower phases of beating directed toward the side of the lesion. The presence of vertical nystagmus elicited by the HSN Test may suggest a central lesion. Limitations: There has historically been a lack of uniformity in the use of the HSN Test. An older form of the test utilized active head-shaking by the patient rather than the now recommended passive technique. Some older studies have used the active head-shaking technique, which may have negatively affected the validity of the test as well as reliability between studies. Also, regarding lack of uniformity of equipment use, many studies of HSN have used either a scleral search coil or ENG equipment, which are not common in the clinical setting. Conversely, fewer studies have utilized infrared lenses or Frenzel glasses, which are more common in modern clinical practice.
Other considerations:
The APTA recommends using the HSN Test in conjunction with other tests, such as the Head Impulse Test (HIT) in order to confirm vestibular dysfunction.
Safety:
oVertebral Artery (VA) Screen should be used prior to HSN Test
§Modified VA testing can be used with older adults who have limited cervical mobility (slight forward lean in sitting, looking back over each shoulder)
oEssential to clear the cervical spine with instability test battery prior to HSN Test
§Of particular use would be the specific tests for integrity of the transverse ligament and rotational instability of C1 on C2, such as the Sharp-Purser Test and the Rotational Alar Ligament Stress Test, respectively.
oThe HSN Test should not be performed if the patient experiences cervical pain with active or passive head/neck movements.
Vestibular nystagmus can be suppressed with light or with visual fixation on a target
oImportance of patient closing eyes during oscillations
oFrenzel glasses are like large magnifying lenses that prevent visual fixation and better visualization of the nystagmus by the clinician.
oInfrared lenses with camera system can prevent light suppression and enable the clinician to better observe the nystagmus, project it on a monitor, and/or record it for later viewing.
Who should I use the Head Shaking Nystagmus Test with?
The Head-Shaking Nystagmus Test can be used with individuals who exhibit signs and symptoms of vestibular hypofunction, including vertigo, disequilibrium, oscillopsia, and general complaints of dizziness or imbalance. The HSN Test is an excellent bedside test for first-line screening of unilateral vestibular hypofunction (UVH), but should be followed with additional rotational and/or caloric testing in order to confirm a patient’s condition.
Evidence for Use of theHead Shaking Nystagmus Test
oUseful as a brief screening tool within a larger test battery for clinicians.
oVestibular dysfunction is more likely when both HSN Test and Head Impulse Test yield abnormal results.
oAbsence of studies establishing reliability of the HSN Test.
The HSN Test was excluded from a diagnostic protocol for dizziness in elderly due to lack of diagnostic accuracy, via Delphi Method of expert opinion consensus (Maarsingh, 2009).
The HSN Test exhibits relatively low sensitivity for UVH as a stand-alone test. (Boniver et al, 2008)
The HSN Test exhibits a 27 % sensitivity and an 85 % specificity (Jacobson et al, 1990).
HSN, as elicited by the HSN Test, showed higher sensitivity for peripheral vestibular lesions than central lesions, compared with other types of spontaneous nystagmus (Vincini et al, 1989).
Resources For Therapists and Healthcare Providers:
Boniver, R., and O.R.L., University of Liège, Verviers, Belgium. "Head-shaking Nystagmus." B-ENT 4.8 (2008): 9-12. Web.
Jacobson GP, Newman CW, Safadi I: Sensitivity and specificity of the head-shaking test for detecting vestibular system abnormalities. Ann Otol Rhinol Laryngol. 1990, 99 (7 Pt 1): 539-542.
O’Sullivan, Susan B. Physical Rehabilitation, 6th ed. 2014 F.A. Davis Company. P. 968-982.
Vicini C, Casani A, Ghilardi P: Assessment of head shaking test in neuro-otological practice. ORL. 1989, 51: 8-13. 10.1159/000132775.
The Head-Shaking Nystagmus (HSN) Test is a screening test used to identify unilateral vestibular hypofunction. It is appropriate for community-dwelling adults and older adults who exhibit signs and symptoms of vestibular dysfunction.
Objectives:
General Information
Head-shaking nystagmus (HSN) is latent, spontaneous eye movement elicited by rapid passive head shaking around a longitudinal axis. The HSN Test is a well-known clinical tool used to help confirm the presence of unilateral vestibular hypofunction.
Procedure:
Interpretation of positive test:
If nystagmus is not present, normal vestibular function is indicated. If nystagmus is present, however, an asymmetry between the left and right peripheral vestibular inputs may be present. Typically, if unilateral vestibular hypofunction is present, eye movement will manifest as horizontal nystagmus, with the slower phases of beating directed toward the side of the lesion. The presence of vertical nystagmus elicited by the HSN Test may suggest a central lesion.
Limitations:
There has historically been a lack of uniformity in the use of the HSN Test. An older form of the test utilized active head-shaking by the patient rather than the now recommended passive technique. Some older studies have used the active head-shaking technique, which may have negatively affected the validity of the test as well as reliability between studies. Also, regarding lack of uniformity of equipment use, many studies of HSN have used either a scleral search coil or ENG equipment, which are not common in the clinical setting. Conversely, fewer studies have utilized infrared lenses or Frenzel glasses, which are more common in modern clinical practice.
Other considerations:
Who should I use the Head Shaking Nystagmus Test with?
The Head-Shaking Nystagmus Test can be used with individuals who exhibit signs and symptoms of vestibular hypofunction, including vertigo, disequilibrium, oscillopsia, and general complaints of dizziness or imbalance. The HSN Test is an excellent bedside test for first-line screening of unilateral vestibular hypofunction (UVH), but should be followed with additional rotational and/or caloric testing in order to confirm a patient’s condition.
Evidence for Use of the Head Shaking Nystagmus Test
Resources For Therapists and Healthcare Providers:
Resources For Patients:
References